OPIIIOCTEN. 53 



OPIIIOCTEN LuTKEN. 



Disk thick and circular, without notches where the arms join it ; 

 partly covered \)y primary plates and racHal shields, ))etween which are 

 fine, close set ^j^rains, or small scales, covering the squamous coat; on 

 the inter])rachial spaces below, a sim})le s(|uamous coat, without any 

 covering of grains. A row of papilhe, j)assing along the genital slits, 

 and upwards, along the margin of the disk, over the arm. Some ol' the 

 basal upper arm-plates l)earing papilliX) along their outer edge. Disk 

 cut away at the l)ase of the arm, so as to form a little arch over one or 

 two upper arm-plates which are within the margin of the disk. Side 

 arm-j)lates meeting below^, but not above. Teeth. Mouth-papilla3. No 

 t()()th-i)apilla>. Arm-spines arranged along the outer edge of the side 

 arm-plates. Two genital slits, beginning at the sides of the mouth- 

 shields. 



Ophiocten Kroyeri Lutkex. 



Ophiocten Kroi/eri LI'tkkx. Vidcnsk. INIfddclt'lser. Nov., 1854. 

 Op/iiiim sei'icea? Forbks. Sutlicrland's Journal of a Journey. 

 Ophiocten Kroijeri Lutkkx. Addit. ad Hist. Oph., j). 52. 



Special Marks. — Arms three to four times the length of the diam- 

 eter of the disk ; two upper arm-spines much the longest ; papilla? of 

 arm-comb continuous ; first, second, and third upper arm-plates bearing 

 papilhv ; sometimes, also, the fourth. 



Descrijitlon of a Specimen. — Diameter of disk, 8.7"™' ; from outer 

 side of mouth-shield to outer corner of opposite mouth-slit, 4.2"""' ; width 

 of arm without spines, 1.9""°' ; length of arm, 31°"°' ; distance from outer 

 side of mouth-shield to inner points of mouth-papilla?, to that betw^een 

 outer corners of mouth-slits, 2.5 : 1.0. Moutli-papilhv, seven or eight to 

 each angle of the mouth ; close set, and making an even row ; outer 

 one very much the widest, Hat, straight, angular ; the next two (or 

 three) similar in shape, but nuich narrower, and more rounded or 

 ])()inted, innermost one lying directly below teeth, and similar to them, 

 being shaped like a very short, thick, blunt spear-head. Teeth six, set 

 close one a])ove the other, longer than broad, flat, pretty thick, Avith a 

 blunt point inward ; uppermost one narrower than those below. Mouth- 

 shields longer than broad, bounded without by a long, ovoid curve, and 

 within presenting an angle ; length to breadth, 1.7 : 1.3. Side mouth- 

 shields meeting within, extremely narrow, but swelling at their outer 

 end into a little knob. Under arm-plates very short, by reason of the 



